The G20 summit seems certain to demonstrate that for most world leaders the conversion to Keynesian economics is no more than skin-deep. The global crisis may have compelled some re-assessment of the “free” market doctrines previously thought to be unchallengeable, but many of those attending the summit are reluctant to accept the responsibilities that a Keynesian approach would require of them.

It is worth rehearsing therefore what the global recession now demands of governments if we are to avoid a further plunge into full-scale depression. Like so much of Keynes’ approach, the prescription rests on common sense rather than ideological prejudice or mathematical models.

The key feature of a recession is a shortage of demand or purchasing power in the economy. The danger is that, once that condition applies, it feeds upon itself. Despite the urgings of politicians, individual actors in the economy – both in their personal lives and in their businesses – understand that times are hard and that the economy is flat or shrinking, and they act accordingly in their own self-interest. They cut their personal spending and their business costs. They employ fewer people and they invest less. Their concern is entirely for their individual or family or business interests.

They cannot be criticised for this. Their behaviour is entirely rational. The problem is that the sum total of all these individual decisions is that the economy shrinks further – a kind of multiplier in reverse.

An economy left to resolve this for itself will take a long and damaging time to come right. If the process is to be short-circuited, and depression is to be avoided, there is only one agency that is capable of taking effective action. That agency is the government.

Only governments have the capability and the duty to act in the wider interest, to take decisions that would be directly contrary to their self-interest if they were individuals or businesses, and to act consciously to defy market logic by spending when others can and will not. Governments can afford to do this, if they choose, because their ability to borrow to fund investment for the future is – by the standards of any other agency – virtually unlimited, and their responsibility is not to particular economic actors, like banks or shopkeepers, but to the economy as a whole. They alone can afford to take a long view – long enough to live with a growing deficit while the economy regains its buoyancy.

It is governments in the end, not banks, who are the funders of last resort. If there was ever any doubt about this, it must surely have been put to rest by the collapse of the banks in most parts of the world, and the taxpayer-funded bail-outs that governments have had to organise. Why, then, are political leaders still so reluctant to recognise that is they, not the banks, who must provide the kind of stimulus to spending that is needed if we are to turn the recession round?

The reason is that they are still prisoners of the same intellectual straitjacket that created the crisis in the first place. Despite all the evidence to the contrary, they are still convinced that the major decisions in the economy should be taken by banks – or the private sector more generally – rather than governments. Even when they have spent billions on bail-outs, and the billions have disappeared into the banks’ balance sheets, they still somehow expect that the banks’ self-interested pursuit of their shareholders’ interests will revive the economy as a whole.

Old habits die hard. Privately owned banks have been allowed to develop a virtual monopoly of credit creation for more than 200 years. It is such a familiar feature of our landscape that it has been scarcely remarked, even when bank credit became by far the most significant element in the rapid growth of the money supply – and therefore the greatest factor in inflation. The banks’ impact on monetary policy – and the exclusive focus on that monetary policy – was itself a huge abdication of responsibility in favour of private interests. But just to make absolutely sure that the banks would not only monopolise credit creation but would also control monetary policy itself, governments surrendered the task they had been elected to fulfil by handing monetary policy over to an “independent” central bank.

Our politicians are still at it. We are told that we must give the banks some “breathing space”. That is after they have walked away with billions of our money. It does not seem to have occurred to our political leaders that it was not the interests of bank shareholders and the survival of banks as institutions that mattered. The focus of policy should have been, first, the security of deposits, and secondly, a re-thinking of whether the banking function should remain a private monopoly or should be seen properly as a public responsibility – as, de facto, it has become. If governments – for which read us – have had to put up the money, why should we not call the shots?